1. Field of Invention
This invention pertains to an apparatus to sense seated occupants for a vehicle occupant restraint system. More particularly, this invention pertains to the use of sensors to measure seat deflection, and the use of electrical signals to determine if the person's weight and seating position are such that an airbag should be deployed.
2. Description of the Related Art
Air bags are important safety devices in modern motor vehicles. There have been, however, injuries associated with the actuation of air bags located in front of and to the side of the passenger seats of vehicles. The occupant of a passenger seat may be injured by the air bag if the occupant is a baby or child in a child seat, a small child, or a child or adult seated too close to the air bag on the front portion of the seat. Attempts to prevent actuation of air bags under unfavorable circumstances are known in the art.
U.S. Pat. No. 6,015,163, titled “System for Measuring Parameters Related to Automobile Seat,” issued to Langford et al. on Jan. 18, 2000, discloses a system that determines whether an air bag should be deployed in the case of an automobile crash. The system uses flexible potentiometers placed in an X-Y grid to determine the weight and position of a person. Position and weight are determined by monitoring a group of flexible potentiometers, each positioned between two turns of a coil spring 74 in or under a seat cushion or seat surface. Langford also discloses a flexible potentiometer attached to the main surface of a leaf spring 100. As a load or force is applied to the spring, the flexible potentiometers produce a resistance change.
U.S. Pat. No. 5,474,327, titled “Vehicle Occupant Restraint with Seat Pressure Sensor,” issued to Schousek on Dec. 12, 1995, discloses a system that disables actuation of an air bag when an occupant weight that is less than a minimum weight and/or a weight center is forward of a reference line. The seat occupant sensing system includes a voltage divider, having a fixed resistor 26 in series with a pressure sensor or variable resistor 28. Each sensor is mounted between polymer film sheets and includes a pair of conductive electrodes separated by a carbon layer such that the resistance between the electrodes changes as pressure changes. The type of variable resistor is not discussed.
U.S. Pat. No. 6,161,439, titled “Seat Belt Tension Prediction,” issued to Stanley on Dec. 19, 2000, discloses a seat belt tension prediction system which includes an accelerometer and a seat weight sensor. The seat weight sensor includes a plurality of force sensitive resistive elements 42 which provide a variable electrical resistance responsive to the amount of force acting on the elements 42. The type of force sensitive resistive element is not disclosed.
U.S. Pat. No. 6,092,838, titled “System and Method for Determining the Weight of a Person in a Seat in a Vehicle,” issued to Walker on Jul. 25, 2000, discloses the use of load sensor beams to detect a person seated in a vehicle seat. Strain gauges 104a-d, which are variable resistance strain gauges, are used to quantify the weight of the person sitting on the seat.
U.S. Pat. No. 6,513,830, titled “Method and Appartus for Disabling an Airbag System in a Vehicle,” issued to Breed et al. on Feb. 4, 2003 discloses a method and apparatus for determining the position of a seat using a potentiometer 601. The potentiometer 601 is positioned along the seat track 602, and a sliding brush assembly 603 is used to determine the fore and aft location of the seat 610.
U.S. Pat. No. 5,232,243, titled “Occupant Sensing Apparatus,” issued to Blackburn et al. on Aug. 3, 1993, discloses an occupant sensing apparatus having an occupant sensor 60 located in the bottom cushion 42 of an automobile seat 34. The occupant sensor 60 is a multi-layer piezoelectric film sensor 110.